Tempered stemware and process of making it

ABSTRACT

Footed glassware is, for the first time, satisfactorily tempered by annealing hollow glassware, such as goblets and blowing them with air jets. The annealing raises the surface temperature of the stemware to about 660* to 680* C. in the cup and to about 490* to 500* C. in the midlength of the stem. The new glass is of superior resistance to mechanical and thermal shocks.

United States Patent Inventor Rene D'Orellce Salnt-Jean-de-la-Ruelle,France Appl. No. 785,168 Filed Dec. l9, I968 Patented Sept. 28, I97!Assignce Compaznle de Salnt Goblin Neuilly-Sur-Selne, France PriorityDec. 22, 1967 France PU 133,535

TEMPEIED ST EMWARE AND PROCESS OF MAKING l1 5 Claim, l Drawing Flu.

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[56] References Cited UNITED STATES PATENTS 2,254,227 9/ l94l Lewis I I52,344,630 3/1944 Mylehrecst 65/] I5 Primary Examiner-Arthur D. KelloggAtrorney-Bauer and Seymour ABSTRACT: Footed glassware is, for the firsttime, satisfactorily tempered by annealing hollow glassware, such asgoblets and blowing them with air jets. The annealing raises the surfacetemperature of the stcmware to about 660 to 680 C. in the cup and toabout 490 to 500 C. in the midlength of the stem. The new glass is ofsuperior resistance to mechanical and thermal shocks.

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RENE dOREFICE ATTORNEYS Y PATENTEDsarzamn v 350 755 sum 3 0P4 INVENTOR.

RENE d'OREFICE ATTORNEYS T EMPERED STEMWARE AND PROCESS OF MAKING IT Thepresent invention relates to tempering stemware in glass of whichgoblets having cup, stem and foot of differing thicknesses areexemplary. Tempered stemware is believed to be a new product. Theinvention also relates to a novel method of making such stemware.

The tempering of glass is accomplished by heating the glass to atemperature approaching its softening point and chilling it rapidly to atemperature strain point. This sets up an internal condition of tensionand an external condition of compression which imparts great strength tothe glass. Tempering has long been carried out with satisfactory resultson flat glass and on tumblers which have reasonable uniformity ofthickness but the tempering of glass objects of which the thicknessvaries greatly has been accompanied by great difficulty and lack ofsuccess. The processes of internal mobility of the glass during thermaltempering are related to the thicknesses of the objects being temperedand if the different parts of the object have different thickness thedifferent internal mobility which is imparted to different portionsdevelops internal strains and unbalanced strains which produce fragilityand frequently immediate rupture. For example, when the known processesfor tempering ordinary drinking glasses which have no feet and no greatdifferences of thickness are applied to stemware or footed pieces inwhich thicknesses vary widely from part to part, failure results.

It is an object of this invention to temper stemware and other hollowglass objects having material differences in thickness. Another objectis to temper stemware with apparatus of the type customarily used in thetempering of tumblers. It will be recalled that in tempering tumblersthe glasses are brought to a temperature on the order of 600 to 700 C.and are blown with cold air jets, usually at room temperature, which aredirected against the inside and outside walls.

Objects of the present process invention are accomplished, generallyspeaking, by a method of tempering glass stemware which comprisesestablishing in the surface thereof a series of temperatures at whichtempering can be accomplished by rapid chilling and which are inverselyproportional to the thickness of the piece, being generally the lower asthe thickness is the greater, and chilling the stemware at a temperingrate. In the present invention prior to the application of the air jetsthe glass is subjected to a thermal treatment such that its surfacetemperature averages 660 to 680 C. in the cup and between 490 and 500 C.in the midportion of the stem. When these temperatures are attained, theglass is blown with the air jets in accordance with accepted tumblerpractice.

The stemware constituting a part of this invention have in all theirparts, cup, foot and stem, a surface compression of at least 410kg./cm."- which is distributed with satisfactory uniformity through allits parts so that if breakage occurs the glass falls into pieces ofwhich the largest dimension is less than 3 cm. This invention is equallyapplicable to holloware which is footed but lacks stems in which thedifferential thickness prevents tempering by ordinary means. Thefollowing description is of the invention as applied to the tempering ofglass goblets. It demonstrates the principles and serves as a preferredmode.

In the drawings, wherein like reference characters refer to like partsthroughout the several views,

FIG. I is a vertical section through a goblet indicating the range oftemperature achieved in the surface before blowing;

FIG. 2 is a diagram of surface temperatures in an operation similar tothat of FIG. I;

FIG. 3 is a vertical section through a goblet undergoing tempering;

FIG. 4 is a plan view of the support of FIG. 3;

FIG. 5 is a diagram indicating the mechanical resistance to shock of thenovel glassware of this invention compared to identical glass annealedbut not tempered;

FIG. 6 illustrates the test of shock resistance by free fall, being avertical section through such apparatus in operation;

FIG. 7 is a graph illustrating the shock resistance of the new stemwarecompared to identical but untempered stemware;

FIG. 8 is a graph illustrating the resistance of the new glassware tothermal shock, in comparison to identical glassware annealed butuntempered;

FIG. 9 is an elevation illustrating the breaking pattern of the temperedglass of this invention; and

FIG. 10 is a bottom view of the foot of the glass of FIG. 9;

The footed glassware represented in the drawings is of the typesometimes called balloon and sometimes called goblet. It is made ofwhite, ordinary soda-lime glass having a thermal coefficient ofexpansion of 87Xl0". It includes a cup I, a foot 2 and a stem 3. Thediameter of the stem is over four times the thickness of the upper partof the cup. The length of the stem is unimportant, the invention beinguseful regardless of its length, whether long or short to the point ofnonexistence.

The glass is first heated so as to bring the surface temperature of itsdifferent parts within the ranges indicated. This can be accomplished bythe use of flame jets of different temperatures or by flame jets of thesame temperature applied to different parts from different distances. Inthe preferred mode, of which the illustrated goblet is representative,the thermal treatment consisted in annealing the glass for 3 minutes l5seconds in an electric furnace having a temperature of 720 C. Thus, onlyone temperature was applied but the desired temperature gradient wasattained by limiting its duration. At the outlet of the furnace thesurface temperatures were measured at 11 different points, from In to[In on FIGS. I and 2, the values at each point being recorded on thefigures. The average temperature of the cup, calculated by averaging thetemperatures of points la to 5a was equal to about 672 C. and

the average temperature of the midpart of the stem, averaged betweenpoints 5a and 9a was about 495 C. At these temperatures the glass wasimmediately transferred to the blowing enclosure of the type habituallyused for tempering tumblers, wherein, as indicated in FIG. 3 at numeral4, the glass rested on the support 5 provided with crossed rods 6 uponwhich it rested, being centered by buffers 7 so as to limit surfacecontact with the support to a minimum and so as to prevent the markingof the glass by the support. The walls of the enclosure 4 are providedwith blowing orifices 4a directed upon the outside of the stemware. Thejets were at room temperature at a relative pressure of 50 mm. ofmercury. A blowing box 8 was disposed above the glass and coaxially withthe enclosure 4. The blowing box was provided with blowing nozzles 8awhich blew jets of air at room temperature at a pressure of I20 mm. ofmercury into the cup 1. Under these circumstances, the footed glasswaredeveloped a surface compression throughout of at least 410 kgJcm. andthey were endowed with thermal and mechanical resistance far superior tothat of the same glass not tempered but which had been subjected to thesame annealing process. The values of these tests are shown in FIGS. 5to 8 wherein the results corresponding to untempered glass arerepresented by curve C in dash lines and the results corresponding tothe tempered stemware in curves C, and C of which the conditions appliedin C, differed somewhat from those applied in C The curve C, records thetesting of goblets of which the rim was I6 mm. from the box 8 duringtempering, while curve C represented the result where the rim wasdisposed 8 mm. from the box.

In FIG. 5 are shown the'results of classical mechanical resistance testsaccording to the Preston system. In that test, the cups of the stemwareare struck at midheight by a pendulum. In the drawing, the percentagesof broken glass are shown in ordinates and the force exerted by thependulum in kilogramcentimeters in abscissas. These tests demonstratedthat the new glassware is much more resistant than that which has notbeen so treated. For example, for a shock of 2 kilogram-centimeters 10percent of the untreated glass broke but none of the tempered glass. Fora shock of 3 kcm. about a third of the untreated glass broke as against10 percent of the tempered. For a shock of 4 kcm. 65 percent of theuntempered glass broke as against 40 to 50 percent of the temperedglass. At a force of 7 kilogram-centimeters all the untempered glassesbroke, whereas it was necessary to increase the force of the stroke to 8and 9 kilogram-centimeters respectively, to break all the temperedglasses.

The improved strength of the tempered glasses of this invention isequally shown by free fall tests. In such tests, the goblet is allowedto fall from different heights H (FIG. 6) through a guide tube 10 upon asteel block 11 of 30 mm. thickness which rests on a cement base 12. FIG.7 shows the results of these tests, wherein the percentages of brokenglasses are carried in ordinates and the height of the fall inabscissas. The tempered glasses are far more resistant than theuntempered, it being noted that the latter had a percent breakage for a10 cm. fall against 0 and 2 percent for the tempered glasses. At aheight of 20 cm. there was 85 percent breakage and at 30 cm. it becameI00 percent for the untempered glasses, whereas at the same heights thebreakage of tempered glass was respectively, 4 and 13 percent and and 34percent.

The new glassware was also subjected to thermal shock, again beingtested against annealed but untempered glass of the same composition. Inthese tests the glasses were raised to a selected temperature in afurnace and then plunged into a water bath at lower temperature. ln FlG.7, the temperature difference between the water and the glass is shownin abscissas while the percentage of breakage is carried in ordinates.No tempered glass broke at a temperature difference of 130 C., whereasthe untempered glasses had 50 percent breakage at a temperaturedifference of 90 C., the breakage becoming 90percent at a 100 differenceand 100 percent for difference.

The tests show that the invention makes great improvement in the qualityof the glassware. The invention makes tempering available for stemwareand produces a stemware which is superior to that which was previouslyknown. The stemware of this invention breaks in small fragments ofuniform size as illustrated in FIGS. 9 and 10, the largest dimension ofthe fragments being less than 3 cm. in the operating conditionshereinabove set forth.

As many apparently widely different embodiments of the present inventionmay be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments.

What is claimed is:

l. A method of tempering glass stemware comprising cups, stems, and feetwhich comprises heating such ware to temperatures which decrease fromabove 600C. at the rim of the foot to below 500 C. at midstem andincrease thence to a maximum above about 650 C. below the rim of thecup, an chilling the stemware at a tempering rate.

2. A method of tempering glass stemware which comprises annealing theglass under conditions which produce in the cup surface temperatures of660 to 680 C., and 490 to 500 C. in the midportion of the stem, andchilling the stemware at a tempering rate.

3 Tempered glass goblets comprising cups, stems, and feet of differingthickness varying from thinnest at the rim of the cup to thickest at thestem, the stem being on the order of several times the thickness of theupper part of the cup, having surface compression at least equal to 410kg./cm. and fragmenting into pieces less than 3 cm. in their largestdimension.

4. Tempered glass goblets according to claim 3 in which the stems are atleast about four times the thickness of the upper part of the cups.

5. A method according to claim 2 which includes the steps of annealingthe stemware at a temperature and for a time equivalent to about 3minutes 15 seconds at about 720 C., blowing the outside of the stemwarewith air at room temperature and a relative pressure of 50 mm. of Hg.,and blowing the inside of the cup with air at room temperature and apressure of about mm. of Hg.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,6O8Y66 Dated fieptgmber 28, L921 Inventofl Rene D'Orefice It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

On the Title Page, at "[73]" change "Compaznie" to Compagnie at [311",change "PU" to PV Column 3, line 27, change to 120 Signed and sealedthis +th day of April 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Commissioner of PatentsAttesting Officer USCOMM-DC 60376-P69 U 5 GOVERNMENT PRINTING OFFICE IQQO-3GGJSA

1. A method of tempering glass stemware comprising cups, stems, and feetwhich comprises heating such ware to temperatures which decrease fromabove 600* C. at the rim of the foot to below 500* C. at midstem andincrease thence to a maximum above about 650* C. below the rim of thecup, and chilling the stemware at a tempering rate.
 2. A method oftempering glass stemware which comprises annealing the glass underconditions which produce in the cup surface temperatures of 660* to 680*C., and 490* to 500* C. in the midportion of the stem, and chilling thestemware at a tempering rate.
 3. Tempered glass goblets comprising cups,stems, and feet of differing thickness varying from thinnest at the rimof the cup to thickest at the stem, the stem being on the order ofseveral times the thickness of the upper part of the cup, having surfacecompression at least equal to 410 kg./cm.2 and fragmenting into piecesless than 3 cm. in their largest dimension.
 4. Tempered glass gobletsaccording to claim 3 in which the stems are at least about four timesthe thickness of the upper part of the cups.
 5. A method according toclaim 2 which includes the steps of annealing the stemware at atemperature and for a time equivalent to about 3 minutes 15 seconds atabout 720* C., blowing the outside of the stemware with air at roomtemperature and a relative pressure of 50 mm. of Hg., and blowing theinside of the cup with air at room temperature and a pressure of about120 mm. of Hg.